MSACL 2022 Abstract

Improving Accuracy and Speed of MALDI MSI for Clinical Translation

Sylwia Stopka (1), Daniela Ruiz (1), Michael S. Regan (1), Nathalie Y.R. Agar (1,2,3) and Sankha S. Basu (4)
(1) Department of Neurosurgery, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts 02115, United States (2) Department of Radiology, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts 02115, United States (3) Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115, United States (4) Department of Pathology, Brigham and Women’s Hospital, Harvard Medical School, Boston, Massachusetts 02115, United States

Sankha (Bobby) Basu, MD, PhD (Presenter) Brigham and Women’s Hospital

Presenter Bio: Sankha (Bobby) Basu, MD, PhD received his BS in Biology and Chemical Engineering in 2003 at MIT and obtained his MD and PhD (Pharmacology) degrees in 2013 from the University of Pennsylvania School of Medicine. His thesis work involved the development and application of stable isotope LC-MS/MS methods to study mitochondrial disease, which was conducted in the laboratory of Dr. Ian Blair. He then went back to Boston to complete a residency in Clinical Pathology and a fellowship in Medical Microbiology at the Brigham and Women's Hospital (BWH). Following his clinical training, he joined the laboratory of Dr. Nathalie Agar at BWH as a post-doctoral research fellow working on a variety of applications including intraoperative MS and MALDI MSI. He recently joined the faculty at BWH as Assistant Director of Clinical Chemistry and Mass Spectrometry and Instructor of Pathology at Harvard Medical School. His clinical roles include the development and implementation of LC-MS methods in clinical chemistry and MALDI TOF based microbial identification in microbiology. Additionally, he continues his work with the Agar lab on clinical and translational applications of MS.

Relevant Financial Disclosures (within past 24 months, reported on Feb 24, 2022) No relevant financial relationship(s) to disclose. Discussing Products? NO, presenter will NOT present educational content related to products/services of the ineligible company(ies) listed above. Conflict mitigation NOT REQUIRED.

INTRODUCTION:
Translation of mass spectrometry into clinical chemistry and microbiology laboratories has been achieved through improvements in several key analytical parameters, including speed and accuracy. Similar improvements are needed for matrix assisted laser desorption ionization mass spectrometry imaging (MALDI MSI) to move into the clinical arena for tissue-based diagnostics. Here we present two methodological advancements in MALDI MSI, which make it more suitable for clinical application.

METHODS:
To improve precision, accuracy and clinical feasibility for drug and metabolite measurements on tissues, we developed a method using tissue microarray (TMA) molds to create calibration curves for several endogenous metabolites. Serial dilutions of analytical standards for adenosine, AMP, ADP, ATP, glutamate were made in gelatin molds generated from TMA templates, layered on a tissue mimetic section and mounted to conductive target slides. Different diluents were evaluated to optimize imaging and stable isotope standards were also evaluated for analytical performance. Calibration curves, along with accompanying tissue sections were imaged using a 15T FT-ICR MS or timsTOF instruments (Bruker). In addition, we applied our recently described rapid MALDI method based on matrix pre-coating and a high laser frequency for the imaging of clinical breast cancer samples.

RESULTS:
Using tissue mimetics in TMA molds allowed for a much higher number of calibration curves and analytes to be accurately measured on a single slide. Furthermore, we found that using collagen improved imaging by reducing diffusion of analytes into the gelatin mold. All analytes demonstrated a high degree of linearity across a wide dynamic range and was used to quantify tissue levels in both animal and clinical samples. The rapid MALDI MSI method was also performed on clinical breast cancer samples, and demonstrated significant metabolic differences within the specimen, highlighting the benefit of a higher spatial resolution approach.

CONCLUSIONS:
We present here parallel advancements in MALDI MSI methods to improve precision, accuracy, and speed of analysis. Future directions will include the integration of multiplex calibration with the short turnaround times of the rapid MALDI MSI method. These advancements will contribute to translation to the clinical laboratory.